Problem: Michael starts counting at 45, and he counts by fives. If 45 is the 1st number that Michael counts. what is the 13th number that he counts?
What is the first number that he counts? $45$ What is the second number that he counts? $\begin{align*}&45 + 5 \\ &= 50\end{align*}$ What is the third number that he counts? $\begin{align*}&45 + 5 + 5 \\ &= 45 + (2 \times 5) \\ &= 55\end{align*}$ What is the 13th number that he counts? $\begin{align*}&45 + (12\times5) \\ &= 45 + 60 \\ &= 105\end{align*}$